Polymers are often distinguished from other materials because they tend to have special challenges when mixing them, such as having to be melted at relatively high temperatures before they can be mixed, and often being very viscous and sticky in their molten state. Most polymers also have a narrow window in time to complete the mixing operation at the elevated temperature before they begin to degrade.
By and large polymers (e.g. thermoplastics) are mixed commercially via what is commonly referred to as continuous processing equipment, such as production type extruders and injection molding machines. Whereby the desired polymer is continually fed into such machines, usually along with some other additive, such as a colorant or filler, where it is melted and mixed with the said additive during the process of forming it into a desired shape, such as a plastic injected molded part, or an extruded profile.
These systems and machines work well for producing many parts very quickly, but are typically large in size, weighing thousands of pounds, and require extensive set-up time and rigorous process control to operate, and are very expensive.
These attributes also make them very difficult and inconvenient to use if one wishes to make just one part or a few parts for evaluation or testing purposes. Testing and evaluating a polymer before attempting to use it commercially in a product is almost always a prerequisite, so regardless of the cost and inconvenience, it is usually done. Additionally, scientists and researchers are greatly hindered in their attempts to quickly develop and test new polymer formulations and mixtures when they are forced to use these large production machines to melt, mix and mold their test samples.
There are companies who have attempted to address this problem with varying degrees of success. Some have created essentially mini versions of production line equipment allowing it to be used in a laboratory environment to melt and mix the polymers and then either extrude the mixed material into a desired profile or form it into an injection molded part. Others have created stand alone machines and devices, also suitable for use in a laboratory environment to melt and mix a desired polymer, and then expel it in molten form, so the user can evaluate the mixed material. Although the line between a stand-alone melt and mixing machine and a mini-production system is somewhat blurred because some systems are comprised of multiple machines or apparatuses that are either used in cooperation with each other or attached together as add-on pieces of equipment for further downline processing of the mixed molten polymer.
Some equipment and systems known to the applicant for melting, mixing and processing polymers on a laboratory scale are as follows:
The “Mini-Compounder KETSE 12/36” manufactured and sold by C. W. Brabender® Instruments, Inc. located in South Hackensack, N.J., USA
The “LME Laboratory Mixing Extruder” manufactured and sold by Dynisco, located in Franklin, Mass., USA
The “LMM Laboratory Mixing Molder” manufactured and sold by Dynisco, located in Franklin, Mass., USA
The “RCP-0250 Microtruder” manufactured and sold by Randcastle Extrusion Systems, Inc., located in Cedar Grove, N.J., USA
The “DSM Xplore 5 ml Micro-compounder” manufactured and sold by DSM Xplore located in the Netherlands.
The “DSM Xplore Micro Injection Moulding Machine” manufactured and sold by DSM Xplore located in the Netherlands.
The “MicroInjector” manufactured and sold by DACA Systems located in Goleta, Calif., USA.
The “Microcompounder” manufactured and sold by DACA Systems located in Goleta, Calif., USA.
The “Thermo Scientific Haake MiniLab II Micro-Compounder” manufactured and sold by Thermo Scientific, located in Waltham, Mass.
Also known is an academic paper (published in Polymer Engineering and Science, January 2001, Vol. 41 No. 1) entitled: “Improving Polymer Blend Dispersions in Mini-mixers” by Milan Maric and Christopher W. Macosko. The researchers in that study evaluated several different laboratory size polymer mixing systems and machines on the market and compared them against each other, noting some of the shortcomings of each.
Although the apparatuses and systems on the market today may be suitable for their intended purposes, they all fall short of most users' desires in some way. The mini-production line systems are still very expensive and still require a significant amount of process control to operate. They are also cumbersome to clean and maintain and take up a lot of laboratory space. The stand-alone machines are also expensive and although smaller, they are also difficult to clean and maintain, plus they carry additional limitations and drawbacks, such as in some cases producing inferior mixing quality.
In any case, it is clearly evident there still remains a great unmet need for a simpler, more affordable, easier to operate, easier to clean and maintain, versatile, robust system that can melt, mix and process polymers in a laboratory environment with consistent high quality. What is disclosed hereafter is the answer to that great unmet need.